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cex: display shifts before reductions

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When reporting counterexamples for s/r conflicts, put the shift first.
This is more natural, and displays the default resolution first, which
is also what happens for r/r conflicts where the smallest rule number
is displayed first, and "wins".

* src/counterexample.c (counterexample): Add a shift_reduce member.
(new_counterexample): Adjust.
Swap the derivations when this is a s/r conflict.
(print_counterexample): For s/r conflicts, prefer "Shift derivation"
and "Reduce derivation" rather than "First/Second derivation".

* tests/conflicts.at, tests/counterexample.at, tests/report.at: Adjust.
* NEWS, doc/bison.texi: Ditto.
This commit is contained in:
Akim Demaille
2020-07-12 18:53:30 +02:00
parent 78f72a4516
commit 4f9ae5de07
7 changed files with 146 additions and 128 deletions
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34
src/counterexample.c
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@@ -76,17 +76,29 @@ typedef struct
{
derivation *d1;
derivation *d2;
bool shift_reduce;
bool unifying;
bool timeout;
} counterexample;
static counterexample *
new_counterexample (derivation *d1, derivation *d2,
bool shift_reduce,
bool u, bool t)
{
counterexample *res = xmalloc (sizeof *res);
res->d1 = d1;
res->d2 = d2;
res->shift_reduce = shift_reduce;
if (shift_reduce)
{
// Display the shift first.
res->d1 = d2;
res->d2 = d1;
}
else
{
res->d1 = d1;
res->d2 = d2;
}
res->unifying = u;
res->timeout = t;
return res;
@@ -107,7 +119,7 @@ print_counterexample (counterexample *cex, FILE *out, const char *prefix)
prefix, cex->unifying ? _("Example") : _("First example"));
derivation_print_leaves (cex->d1, out, prefix);
fprintf (out, " %s%-20s ",
prefix, _("First derivation"));
prefix, cex->shift_reduce ? _("Shift derivation") : _("First derivation"));
derivation_print (cex->d1, out, prefix);
// If we output to the terminal (via stderr) and we have color
@@ -120,7 +132,7 @@ print_counterexample (counterexample *cex, FILE *out, const char *prefix)
derivation_print_leaves (cex->d2, out, prefix);
}
fprintf (out, " %s%-20s ",
prefix, _("Second derivation"));
prefix, cex->shift_reduce ? _("Reduce derivation") : _("Second derivation"));
derivation_print (cex->d2, out, prefix);
fputc ('\n', out);
@@ -506,7 +518,7 @@ example_from_path (bool shift_reduce,
: shortest_path_from_start (itm2, next_sym);
derivation *deriv2 = complete_diverging_example (next_sym, path_2, NULL);
gl_list_free (path_2);
return new_counterexample (deriv1, deriv2, false, true);
return new_counterexample (deriv1, deriv2, shift_reduce, false, true);
}
/*
@@ -619,7 +631,8 @@ ss_set_parse_state (search_state *ss, int idx, parse_state *ps)
*/
static counterexample *
complete_diverging_examples (search_state *ss,
symbol_number next_sym)
symbol_number next_sym,
bool shift_reduce)
{
derivation *new_derivs[2];
for (int i = 0; i < 2; ++i)
@@ -630,7 +643,8 @@ complete_diverging_examples (search_state *ss,
new_derivs[i] = complete_diverging_example (next_sym, sitems, derivs);
gl_list_free (sitems);
}
return new_counterexample (new_derivs[0], new_derivs[1], false, true);
return new_counterexample (new_derivs[0], new_derivs[1],
shift_reduce, false, true);
}
/*
@@ -1111,7 +1125,7 @@ unifying_example (state_item_number itm1,
{
// Once we have two derivations for the same symbol,
// we've found a unifying counterexample.
cex = new_counterexample (d1, d2, true, false);
cex = new_counterexample (d1, d2, shift_reduce, true, false);
derivation_retain (d1);
derivation_retain (d2);
goto cex_search_end;
@@ -1149,7 +1163,7 @@ cex_search_end:;
// If a search state from Stage 3 is available, use it
// to construct a more compact nonunifying counterexample.
if (stage3result)
cex = complete_diverging_examples (stage3result, next_sym);
cex = complete_diverging_examples (stage3result, next_sym, shift_reduce);
// Otherwise, construct a nonunifying counterexample that
// begins from the start state using the shortest
// lookahead-sensitive path to the reduce item.
@@ -1226,6 +1240,8 @@ counterexample_report (state_item_number itm1, state_item_number itm2,
free_counterexample (cex);
}
// ITM1 denotes a shift, ITM2 a reduce.
static void
counterexample_report_shift_reduce (state_item_number itm1, state_item_number itm2,
symbol_number next_sym,